Asparagine endopeptidase (AEP), also known as legumain, is a lysosomal cysteine protease that cleaves peptide bonds C-terminally to asparagine residues. AEP is involved in various cellular events, including antigen processing, the cleavage of other lysosomal enzymes, osteoclast formation, and proper kidney functionality. In mammals, AEP is highly expressed in the kidneys; mice deficient in AEP accumulate various proteins in the endosomes and lysosomes of the proximal tubule cells of their kidneys, which results in a pathology consisting of hyperplasia, fibrosis and glomerular cysts. AEP-null mice exhibit symptoms similar to those of hemophagocytic lymphohistiocytosis, suggesting the enzyme is involved in the pathophysiology of this disease. Biochemically, the enzyme is highly regulated by its specificity for asparagine residues and pH. The particular motif that AEP uses to recognize its substrates is not completely understood. Dysregulated AEP activity has been implicated in various diseases, including cancers and neurodegeneration.
Ovat et al. report aza-peptidyl Michael acceptor and epoxide inhibitors as inhibitors of Schistosoma mansoni and ixodes ricinus legumains (asparaginyl endopeptidases). See J Med Chem, 2009, 52, 7192-7210.
Loak et al. report acyloxymethylketone inhibitors of asparaginyl endopeptidase. See Biol Chem, 2003, 384, 1239-1246.
Niestroj et al. report inhibition of mammalian legumain by Michael acceptors and AzaAsn-halomethylketones. See Biol Chem (2002) 383, 1205-1214.
Xiang et al. report DNA vaccines target the tumor vasculature and microenvironment and suppress tumor growth and metastasis. See Immunol Rev, 2008, 222, 117-128.
Cancer cell metastasis is a complex process that involves the tumor microenvironment, which is a contributor to the increased invasiveness and migratory character of neoplastic cells. Malignant cells typically interact with a surrounding ecosystem of cells, including myeloid cells, fibroblasts, tumor-associated macrophages, and endothelial cells, to promote angiogenesis, degradation of the extracellular matrix and cell motility. Throughout tumor progression, many extracellular proteases contribute to the changes that occur in the tumor microenvironment and those most commonly associated with aberrant proliferation and metastasis are the matrix metalloproteinases (MMPs). The zinc-dependent endopeptidases are involved in a variety of cellular processes, including cell signaling, tissue remodeling, organ development and inflammatory response. However, the capability of this enzyme family to degrade the extracellular matrix has implications in cancer cell invasion and metastasis.
Asparagine Endopeptidase (AEP, Legumain) activates MMP-2 (Progelatinase A) by proteolytic removal of an N-terminal propeptide. AEP is a lysosomal cysteine endoprotease and is the mammalian enzyme that cleaves C terminally to asparagine residues. While only a limited quantity of AEP is detected in normal tissues, the enzyme is overexpressed on the cell surface and in cytoplasmic vesicles of solid tumors. The endoprotease activity of AEP has been associated with increased invasive and aggressive behavior of several cancers, including breast, prostate, colorectal and gastric carcinomas. See Gawenda et al., Legumain expression as a prognostic factor in breast cancer patients, Breast Cancer Res Treat, 2007, 102, 1-6; Ohno et al., Association of legumain expression pattern with prostate cancer invasiveness and aggressiveness, World J Urol, 2013, 31, 359-364; Li et al., Effects of legumain as a potential prognostic factor on gastric cancers, Med Oncol, 2013, 30, 621. Haugen et al., Nuclear legumain activity in colorectal cancer, PLoS One, 2013, 8, e52980. Thus, AEP inhibitors represent a promising cancer therapeutic.
Liao et al. report a targeting ligand for nanotherapeutic drug delivery inhibiting tumor growth. Nanomedicine, 2011, 7, 665-673.
References cited herein are not an admission of prior art.